This invention relates to compounds which are useful as reactive coalescents, methods of improving the stability of reactive coalescents, and a process of preparing low molecular weight polymers which are useful as reactive coalescents.
Water based polymers having a low glass transition temperature (xe2x80x9cTgxe2x80x9d) can be formulated into coatings without plasticizers. These coatings often have inadequate hardness for many applications. Many applications, such as gloss and semigloss paint formulations, require the properties of a hard polymer, i.e. a polymer with a Tg significantly above the ambient temperature. To meet these needs, a volatile coalescent or plasticizer is typically used to achieve film formation. The use of these volatile solvents in coatings is coming under scrutiny due to pollution and odor problems.
Attempts have been made to use xe2x80x9creactive coalescentsxe2x80x9d. Reactive coalescents are compounds which aid in film formation similar to the conventional coalescent but are non-volatile and react to become part of the final coating.
U.S. Pat. No. 4,141,868 discloses the use of dicyclopentenyloxyethyl methacrylate (xe2x80x9cDCPOEMAxe2x80x9d) as a reactive coalescent. Vinyl reactive coalescents are reactive coalescents which contain a vinyl group. DCPOEMA, dicyclopentenyloxyethyl acrylate (xe2x80x9cDCPOEAxe2x80x9d), dicyclopentenyloxy acrylate (xe2x80x9cDCPOAxe2x80x9d), and dicyclopentenyloxy methacrylate (xe2x80x9cDCPOMAxe2x80x9d) are examples of vinyl reactive coalescents.
Despite the disclosure, there is a continuing need for stable reactive coalescents for use in coating compositions.
We have surprisingly found that stable reactive coalescents for use in coating compositions can be obtained by altering the structure of the reactive coalescent or adding an inhibitor to the reactive coalescent.
In a first aspect, the present invention provides compounds of formula I: 
Wherein:
R=xe2x80x94(CH2)nR1, xe2x80x94(CH2)2O(CH2)2OH, xe2x80x94(CH2CH2O)2(CH2)3OH, xe2x80x94CH2CH2OCOR2, xe2x80x94(CH2)2O(CH2)2O(CH2)3CH3, xe2x80x94CH2CH(CH3)xe2x80x94OH, xe2x80x94CH2CH2OCO(CH2)4COOR3, dicyclopentenyloxyethane;
R1 is selected from H, OH and CH3;
R2=(C1-C6) straight chain or branched alkyl;
R3 is selected from CH3 and dicyclopentenyloxyethane; and n=2 to 10.
In a second aspect, the present invention provides a process for the preparation of polymers comprising:
providing a compound selected from the group consisting of DCPOEA, DCPOEMA, DCPOA, and DCPOMA;
providing a solvent selected from the group consisting of water, acetone, methanol, isopropanol, propionic acid, acetic acid, toluene, hexane, ethyl acetate, methylethyl ketone, dimethyl formamide, dimethylsulfoxide, and combinations thereof,
providing an initiator;
forming a reaction mixture by admixing the compound selected from the group consisting of DCPOEA, DCPOEMA, DCPOA, and DCPOMA, the solvent, and the initiator; and
passing the reaction mixture through a heated zone wherein the reaction mixture is maintained at a temperature of at least 175xc2x0 C. for from 0.1 seconds to 300 seconds to form a liquid polymer with a number average molecular weight of from 450 to 10,000.
In a third aspect, the present invention provides a method of use comprising:
providing an emulsion polymer;
providing a liquid polymer prepared from a compound selected from the group consisting of DCPOEA, DCPOEMA, DCPOA, and DCPOMA, the liquid polymer having a number average molecular weight of from 450 to 10,000;
forming a coating composition by admixing the liquid polymer having a number average molecular weight of from 450 to 10,000 with the emulsion polymer; and;
applying said coating composition to a substrate wherein the coating composition forms a continuous film on the substrate.
In another embodiment, the present invention provides a composition comprising:
from 1% to 25% of a vinyl reactive coalescent based on a weight reactive coalescent to total weight of composition basis;
from 1 ppm to 10,000 ppm of an inhibitor selected from the group consisting of 4-methoxyphenol, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy, and di-tertiary butyl nitroxyl, based on a weight inhibitor to total weight of composition basis; and
from 74% to 99% of an emulsion polymer based on a weight emulsion polymer to total weight of composition basis.
In another embodiment, the present invention provides a method for improving the stability of a vinyl reactive coalescent comprising:
providing an emulsion polymer;
passing the emulsion polymer through a diafiltration apparatus; and
charging the emulsion polymer which has been passed through the diafiltration apparatus with a vinyl reactive coalescent.
In another embodiment, the present invention provides a coating composition comprising:
an emulsion polymer; and
a compound selected from the compounds of Formula I 
xe2x80x83Wherein:
R=xe2x80x94(CH2)nR1, xe2x80x94(CH2)2O(CH2)2OH, xe2x80x94(CH2CH2O)2(CH2)3OH, xe2x80x94CH2CH2OCOR2, xe2x80x94(CH2)2O(CH2)2O(CH2)3CH3, xe2x80x94CH2CH(CH3)xe2x80x94OH, xe2x80x94CH2CH2OCO(CH2)4COOR3, dicyclopentenyloxyethane;
R1 is selected from H, OH and CH3;
R2=(C1-C6) straight chain or branched alkyl;
R3 is selected from CH3 and dicyclopentenyloxyethane; and n=2 to 10, and a liquid polymer prepared from a compound selected from the group consisting of DCPOEA, DCPOEMA, DCPOA, and DCPOMA, the liquid polymer having a number average molecular weight of from 450 to 10,000.
The inhibitors useful in this invention include hydroquinone (xe2x80x9cHQxe2x80x9d), 4-methoxyphenol (xe2x80x9cMEHQxe2x80x9d), phenothiazine (xe2x80x9cPTZxe2x80x9d), 4-hydroxy-2,2,6, 6-tetramethyl-1-piperidinyloxy (xe2x80x9c4-HTxe2x80x9d), and 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy, are available from Aldrich Chemical Company. Di-tertiary butyl nitroxyl is available from Nova Molecular Technologies, Lake Geneva, Wisconsin. The inhibitors are typically used at levels of from 1 ppm to 10,000 ppm on a weight inhibitor to total weight of the composition basis. Preferred are inhibitor levels of from 100 ppm to 1,000 ppm. More preferred are inhibitor levels of from 200 ppm to 700 ppm.
The reactive coalescents of this invention are prepared by processes known in the art. For example, direct esterification, transesterification or the use of acid halides may be employed to convert alcohols to esters of this invention. Examples of compounds of Formula I include, but are not limited to: dicyclopentenyloxyethyl acetate, dicyclopentenyloxyethyl butyrate, dicyclopentenyloxy-2-(2-hydroxyethoxy)ethane, dicyclopentenyloxy -2-(2-butoxyethoxy)ethane, dicyclopentenyloxyhexanol, dicyclopentenyloxyhexane, dicyclopentenyloxybutane, dicyclopentenyloxy (2-methyl)propane, and 1,2-bis (dicyclopentenyloxy)ethane.
The low molecular weight polymers of this invention may be useful as reactive coalescents, and may be prepared by conventional techniques, such as solution or emulsion polymerization, which are well known in the art. The low molecular weight polymers may also be prepared by the high temperature, low residence time process of this invention. In the process of this invention, a reaction mixture is formed by combining at least one compound selected from DCPOEA, DCPOEMA, DCPOA, and DCPOMA and optionally, compatible monomers with a solvent and an initiator. Suitable solvents include, but are not limited to water, acetone, methanol, isopropanol, propionic acid, acetic acid, toluene, alkanes such as hexane; esters such as ethyl acetate; methylethyl ketone, dimethyl formamide, dimethylsulfoxide, and combinations thereof. The process of this invention may be run in the absence of solvent.
Initiators are compounds which initiate the polymerization of monomers. Suitable initiators for the present invention are any conventional initiators. Among the suitable initiators that may be used are thermal free-radical initiators, such as hydrogen peroxide, certain alkyl hydroperoxides, dialkyl peroxides, persulfates, peresters, percarbonates, ketone peroxides and azo initiators. Specific free-radical initiators include, for example, hydrogen peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, tert-amyl hydroperoxide and methyl ethyl ketone peroxide. The free-radical initiators are typically used in amounts of 0.5 to 25% based on the total monomer weight.
Redox initiator systems may also be used. Redox initiator sytems include reducing agents, for example, sodium bisulfite, sodium sulfite, hypophosphites, phosphites, isoascorbic acid, sodium formaldehyde-sulfoxylate and hydroxylamines, used in conjunction with suitable oxidizing agents, such as the thermal free-radical initiators noted above. The redox initiator systems are typically used in amounts from 0.05 to 10%, preferably from 0.5 to 5%, based on the weight of total monomer. Combinations of initiators may be used.
The process of this invention is typically run at a temperature of from 175xc2x0 C. to 500xc2x0 C. Preferred is a temperature of from 225xc2x0 C. to 450xc2x0 C. It is preferred to conduct the polymerization at a pressure of from 1,000 to 5,000 pounds per square inch (xe2x80x9cpsixe2x80x9d), and more preferably at from 3,200 to 4,200 psi. By low molecular weight polymers is meant polymers typically with number average molecular weights from 450 to 10,000. Preferred are polymers with number average molecular weights from 450 to 5,000. More preferred are polymers with number average molecular weights from 450 to 3,000.
Compatible monomers are monomers which are miscible with DCPOEA, DCPOEMA, DCPOA or DCPOMA. Compatible monomers include, but are not limited to: methyl acrylate, ethyl acrylate, butyl acrylate, t-butylaminoethyl methacrylate, dimethylaminoethyl methacrylate, isobornyl methacrylate, styrene, vinyl toluene, methacrylic acid, methyl methacrylate, butyl methacrylate, isobutyl methacrylate, allyl methacrylate, lauryl methacrylate, and 2-ethylhexyl methacrylate.
The reactive coalescents are typically used at levels of from 1% to 25% on a weight reactive coalescent to total weight of composition basis. Preferred are reactive coalescent levels of from 2% to 20%. More preferred are reactive coalescent levels of from 5% to 15%.
This invention may be applied to any emulsion polymer. The preparation of emulsion polymers is known in the art, see for example U.S. Pat. No. 5,346,954.
The following is a list of products used within this invention and their sources: